Method of producing magnetic core loops for electrical induction apparatus



Oct. 30, 1956 c. a. DUENKE METHOD OF PRODUCING MAGNETIC CORE LOOPS FOR ELECTRICAL INDUCTION APPARATUS Filed March 14, 1952 INVENTOR.

FIG. 6.

United States Patent Oflice 2,768,426 P tented 9s 30, 195.6

METHOD on rnonuonsc MAGNETIC CORE l gog s FOR ELECTRIGAL mnpcrron APPA- e e G- Dhsh e e ster Gra e M0. s ho t9 Moloney Electric Company, St. Louis, 0,, a corpo- 1. 1 odu magn co es o e ti ,1 P Wpllnd construction it has been necessary heretofore to use forms or internal formers of some type to preserve the shapes of the cores. during various steps .in theiprocessing thereof, such, for instance, as strain annealing, han in et -s and t e reseh inven on as o i PI? h s obiss t .is i h o a me d uh a eliminates the need for costly formers with a resultant substantial saving in cost of production and in labor, and the elimination of the cost f heating the added weight of the formers during portions of the manufacturing process which would involve heating.

.Fig. 1 is a side elevation of a core loop constructed in accordance with this invention, showing same s it appears when still in place on the thin: on which t is wqp H 2 .is a perspective view of a form employed in producing a core in accordance with this invention, a part of the form being broken away.

Fig. 3 is a schematic view showing an early stage of the core winding operation when the form shown in Fig. 2 is employed.

Fig. 4 is a perspective view of a stiffening element which may be employed in accordance with this invention.

Fig. 5 is a perspective view of a modified form of a stiffening element which may be employed in carrying out this invention.

Fig. 6 is a schematic view showing the use of the stiffening element illustrated by Fig. 5.

In the drawing, wherein are shown for purposes of illustration, merely, two embodiments of the invention, A designates in Fig. 1 a magnetic core loop made in accordance with this invention. The core loop A is of the continuous, tape wound construction and it is characterized by being provided with a stiffening element 1 located within the window 2 of the core which is formed from material that is capable of withstanding the heat to which the core is subjected. This material E, stainless steel, for instance, has higher hot strength than the magnetic material and therefore the stiffening element does not deform under the high temperatures employed in processing the core loop. By referring to Fig. 1 it will be noted that the stiffening element 1 comprises a pair of parallel walls 3 which are joined by a wall 4 at corresponding edges thereof. The parallel walls 3 at their opposite edges have extended therefrom a pair of relatively short leg portions 5 which extend inwardly toward each other, as is shown to good advantage in Figs. 3 and 4, and the stiffening element 1 is open at its opposite ends. The stiffening element effectively constitutes a slotted rectangular bushing, the wall 4 and divided parts or leg portions 5 of which form oppositely facing supports held apart by web means or walls 3. By providing a core loop with a stiffening element within the window thereof, as described above, the core loop is supplied with sufiicient rigidity to withstand the handling to which it is subjected during processing thereof with- 2 out the use of costly formers for supplying the required i id ty- In producing core loops in accordance with this invention a core winding machine (not shown) is employed and this machine is provided with a form, such as that shown in Fig. 2 and designated by reference character 6 The form 6 of Fig. '2 comprises a body portion 7 in which is formed a pair of parallel slots 8, these slots bein o e t t e r rd e d o the dy port n 7 of the form 6 and being closed at their rear ends, and id l t P vi the fo m th a P of forward y extended form portions 9, and an intermediate forwardly extended form portion l0 which is disposed betweensaid fo m Po t ns .BY ati u n t i s.- an 3 i wil he noted that the intermediate form portion 10 of the form .6 is recessed or depressed at its top and bottom faces, a i ndicat d a i ei g fo a Pu t h hereinafter set forth. The .form 6, which constitutes a three-armed o fo m n w h e t a m v is flanked by arms 9, is provided also with a spindle 12 (h h r a rah ed n coopera on wi a P of the a s winding machine with which the form 6 is associated for core winding operations so, as to cause the form .to .be rstatsd y the are w n n ma n prgducing a core loop in accordance with this in: rem ss he stiffen n element s i d e r a d onto the intermediate form portion 10 of the form ,6, the walls} pfthe stilfening element being disposed in tha st 2 he form ns1 the l 4 d the le nsrtih 5 9t sti en n clem n bei d sposed its sstast wit the app si e depresse fa es P sa in mediate form por'tion. When th'e leading portion the tape has been arranged with respect to the for'rn6, as shown in Fig. 3, the core winding machine is set in motion and the form 6 is rotated. Thus the tape is drawn from a reel (not shown) and is wound on the rotating form to produce the core loop A shown in Fig. l, the free end of the tape being temporarily secured in place by a strip of adhesive tape T.

From the foregoing it is plain that a core loop provided within its window with a stiffening element, such as that designated by the reference character 1 in Fig. '1, is braced so that it is able to withstand the handling and processing to which the core loop is subjected during the production thereof. It is to be understood that the stiffening structure 1 of the core loop A is not a permanent part of the finished core, but, instead, this stitfening structure serves its function only during the processing of the core, after which said stiffening structure is removed from the core window and is disposed of.

In Figs. 5 and 6 a modified form of stiffening element is illustrated for providing a core loop with the rigidity required during processing of the core loop. The stiffening element 13 is of U-shaped formation, being comprised of spaced legs 13a and a transverse or bridge portion 13b which joins said spaced legs. Portion 13b and the outer two edges of legs 13a constitute oppositely facing supports. The spaced legs of the stiffening element are disposed in the slots 8 of the form 6 with the inner face of the bridge portion of the stiffening element contacting with one of the depressed faces 11 of the intermediate portion 10 of said form, as is shown in Fig. 6. A bent end portion 14 of the magnetic tape material from which the core loop is being produced is inserted into one of the slots 8 of the form 6 beside the leg of the stifiening' element 13 which is disposed in the same slot of the form. The core winding machine is then set in motion and the core loop is wound on the rotating form 6.

Attention is directed to Fig. 1 of the drawing wherein spaces are shown between the top face of the left-hand form portion 9 and the adjacent wall of the window 2 of the core loop A, and between the top face of the wall 4 of the stiffening element 1 and said adjacent wall of the window of the core loop. Actually, in a core loop made in accordance with this invention no such spaces will be present as they are the result, merely, of the exaggerated thickness of the magnetic tape material which as a matter of fact is paper thick, this exaggeration of thickness being a drafting requirement.

I claim:

1. The method of producing a magnetic core loop from magnetic tape comprising sliding a bushing having oppositely facing supports held apart by web means into a core form which is recessed and slotted to receive said bushing, said bushing having greater hot strength as related to that of the magnetic tape as to resist deformation of the core loop during heat treatment thereof, winding the tape as a coil around the core form and bushing with its leading end inside, securing the trailing end of the tape to the outside of the coil, separating said core form from the bushing and coil thereby form ing a substantially rectangular central window in said coil with the bushing disposed therein and spaced from two interior surfaces of said coil, said opposite'supports of the web means rigidly bracing the two other opposite interior surfaces of the coil, heat treating said coil and bushing assembly at annealing temperatures, and removing the bushing from said coil window.

2. The method of producing a magnetic core loop according to claim 1, wherein the core form includes several slots and the web means of the bushing is constituted by several webs respectively insertable into said slots.

3. The method of producing a magnetic core loop according to claim 2, wherein the several slots of the core form and the several webs of the bushing are restricted to two each and the bushing is of generally rectangular form.

4. The method of producing a magnetic core loop according to claim 3, wherein the rectangular form of the bushing is constituted by said two webs, a transverse portion forming one facing support and joining the Webs on one side, the facing support on the other side of the Webs being formed of spacedly divided parts associated with the respective webs.

5. The method of producing a magnetic core loop from magnetic tape comprising sliding a slotted rectangular bushing over a central arm of a three-armed core form having two arms flanking said central arm, said bushing having a higher hot strength as related to that of the magnetic tape as to resist deformation of the core loops during heat treatment thereof, inserting the leading end of a length of the tape between one of said flanking arms and said bushing, winding the tape as a coil about the core form and bushing assembly, securing the trailing end of said tape to the outside of the coil, separating said core form from the bushing and coil thereby forming a substantially rectangular central window in said coil with the bushing disposed therein and spaced from two interior surfaces of said coil and supporting the central portion thereof on two other interior surfaces, heat treating said coil and bushing assembly at annealing temperatures, and removing the bushing from said coil window.

References Cited in the file of this patent UNITED STATES PATENTS 1,815,620 Horn July 21, 1931 2,246,240 Brand June 17, 1941 2,313,306 Wiegand Mar. 9, 1943 2,416,989 Gauthier Mar. 4, 1947 2,657,456 Moody Nov. 3, 1953 

